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Title: Phase behaviour of montmorillonite aqueous suspensions and applications in Pickering emulsions
Author: Cui, Yannan
ISNI:       0000 0004 2724 956X
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2011
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This thesis investigates montmorillonite clay particles, which are plate-like and have a hydrophilic surface, a high surface charge and a high specific area. Four studies were carried out and new results relating to polyetheramine adsorption on clay, clay suspension structure and clay-stabilised emulsions are reported. Protonated amines are known to adsorb to clay due to charge interactions. However the adsorption of polymers with primary amine end group at high pH has not previously been studied. We carry out the first such study on the adsorption of polyetheramines at a pH higher than the pKa of the amines. Our results reveal that the adsorption happens via an ion-exchange mechanism. In the adsorption process, the primary amine end-groups get protonated and release hydroxyl ions. The adsorbed molecules adopt a touching mushroom configuration. The effect of the polyetheramine adsorption on the suspension was initially observed due to the obvious change of suspension viscosity. At full coverage of the polyetherarnine, rheological data reveal that the sol/gel transition of the suspension is shifted from 3wt% to 6 wt% clay. Using scattering techniques, large scale string-like structures are found in the bare clay suspensions, which subsequently disappear upon the addition of polyetheramine. This thesis also includes the study of clay particles at interfaces. Surface-modified clay particles are found to stabilise oil-in-water Pickering emulsions. The clay particles at the droplet surface are found to adopt an orientation parallel to the droplet surface, and there are on average four layers of clay particles at the interface. Using Pickering emulsions as a template, well-defined clay microcapsules were prepared by cross-linking the clay particles at the droplet surface. The conclusion on clay orientation is further substantiated by direct observation of the microcapsule surface using SEM.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available